Device for collecting solar radiation

ABSTRACT

A device for collecting solar radiation without guiding the orientation thereof relative to the sun position is disclosed. The device includes at least one photovoltaic solar collector having a face sensitive to the solar radiation, at least one reflecting surface for reflecting the solar radiation towards the sensitive face of the collector, and an orientation apparatus for supporting the solar collector. The orientation apparatus providing an orientation and an inclination to the sensitive face of the collector in relation to the reflecting surface. The reflecting surface is conformed so that, at least during predetermined periods of a day and at least during predetermined days of a year, solar radiation reflected by the reflecting surface reaches the sensitive face of the solar collector with a minimized angle of incidence when the device is arranged in a predetermined orientation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of International Application No. PCT/IB2008/002538, filed Sep. 24, 2008, which was published in the French language on Apr. 9, 2009, under International Publication No. WO 2009/044247 A2 and the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Embodiments of the present invention relate to the field of devices for collecting solar radiation. Nowadays, the devices generally used are arranged in flat panels integrating solar collectors transforming solar energy into electrical energy. The collection ability, and therefore the electrical efficiency, of such panels directly depend on the surface of the sensitive face directly exposed to the sun of the solar collectors, and on the orientation of this face in relation to the solar radiation.

Embodiments of the invention more particularly relate to a device for collecting solar radiation, including at least one photovoltaic solar collector having a face sensitive to the solar radiation, at least one reflecting surface for reflecting the solar radiation towards the sensitive face of the collector, and means for maintaining the solar collector which determine the orientation of the sensitive face of the collector in relation to the reflecting surface.

Devices of the aforementioned type are referred to as “concentrating photovoltaic panels”. In a photovoltaic solar module, the most expensive component is the photovoltaic collector. Interposing a concentrator device between the sun and the collector makes it possible to use a photovoltaic collector with a smaller surface, for the benefit of the cost price of the module. The concentration is generally obtained by a system of parabolic mirrors with solar tracking.

The drawback of concentrating photovoltaic panels is that the angle of incidence of the solar light must be very low so that such panels operate properly only with a system for guiding the panels in relation to the sun travel, generally called solar tracking, so that the panels remain perpendicular to the reflected sun radiation.

U.S. Pat. No. 2,919,298 suggests, for example, to provide a plurality of cup shaped paraboloid mirrors having one focal point and imperatively requiring, due to the shape of the cups and their unique focal point, a system for guiding the cups in relation to the sun so that the solar light vertically reaches the cups, as it is shown in FIG. 1.

U.S. Pat. No. 4,337,758 also describes a photovoltaic device provided with a paraboloid mirror with a complex surface requiring guiding in relation to the sun.

European Patent Publication No. EP 347 443 also describes a solar module with multiple mirrors and multiple solar collectors of the “double face” type, the mirrors being in the shape of grooves with parabolic profiles and thus requiring, to be efficient, that the solar light has a low angle of incidence in relation to the solar module.

Japanese Patent Publication No. JP 2001-127331 also describes a solar panel comprising double face solar collectors, the lower face of which receives solar radiation reflected by flat reflectors (FIG. 1 b) or cup shaped reflectors (FIG. 3). As previously, such a solar panel requires a controlled orientation and must receive the solar light perpendicularly to the surface thereof to yield a satisfying energetic efficiency.

Canadian Patent Publication No. CA 2 428 578 also describes a device including a reflector in aluminum of paraboloid concave shape which is almost entirely covered with double face photovoltaic cells of pyramidal shape. The solar radiation can penetrate into the reflector cup only by the edges of the device, which are provided with a small amount of reflective mercury to that end.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the invention more particularly relate to a photovoltaic device using a reflecting surface, which may be used without guiding the orientation thereof in relation to the sun position.

One embodiment of the invention thus provides a device for collecting solar radiation without guiding the orientation thereof relative to the sun position. The device includes at least one photovoltaic solar collector having a face sensitive to the solar radiation, at least one reflecting surface for reflecting the solar radiation towards the sensitive face of the collector, and an orientation apparatus supporting the solar collector. The orientation apparatus provides an orientation and an inclination to the sensitive face of the collector in relation to the reflecting surface. The reflecting surface is conformed so that, at least during predetermined periods of a day and at least during predetermined days of a year, solar radiation reflected by the reflecting surface reaches the sensitive face of the solar collector with a minimized angle of incidence when the device is fixedly arranged in a predetermined orientation relative to Earth.

According to one embodiment, the solar collector is of longitudinal shape and the reflecting surface is conformed so that, at least during some periods of a day and at least during some days of the year, reflected solar radiation reaches the sensitive face of the solar collector with a minimized angle of incidence for an approximate North-South orientation of the longitudinal axis of the solar collector.

According to one embodiment, the solar collector is of longitudinal shape and the reflecting surface has, in a section plane perpendicular to the longitudinal axis of the collector, a first profile with no vertical axis of symmetry.

According to one embodiment, the solar collector is of longitudinal shape and the reflecting surface has, in a longitudinal section plane parallel to the longitudinal axis of the collector, a second profile with no vertical axis of symmetry.

According to one embodiment, the sensitive face of the solar collector is disposed above a longitudinal edge of the reflecting surface with a determined inclination angle.

According to one embodiment, the solar collector is of longitudinal shape, and the device includes first and second reflecting surfaces symmetrically arranged relative to a longitudinal plane of the device.

According to one embodiment, the sensitive face of the solar collector is arranged above a longitudinal junction area of the first and second reflecting surfaces.

According to one embodiment, the device includes first and second solar collectors of longitudinal shape, the first solar collector having its sensitive face directed towards the first reflecting surface with a first inclination angle, the second solar collector having its sensitive face directed towards the second reflecting surface with a second inclination angle.

According to one embodiment, the device includes a cavity receiving the reflecting surface and the solar collector is fixed on a support projecting into the cavity.

According to one embodiment, the device includes a cavity receiving the reflecting surface and a cover transparent to the solar radiation, covering the cavity.

According to one embodiment, the solar collector is fixed on the cover.

According to one embodiment, the projection of the surface of the solar collector into a plane above the device is between about 5% and 30% of a projection of the reflecting surface into the same plane.

According to one embodiment, the device includes a coupling apparatus configured to fix the device to at least one of another adjacent device or a structure.

According to one embodiment, the device includes an electrical connector configured to link the solar collector to an exterior of the device.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.

In the drawings:

FIG. 1 shows a cross section of an embodiment of a device according to the invention;

FIG. 2 shows a magnified cross section of the central part of the device of FIG. 1;

FIG. 3 is a top view of the device of FIG. 1;

FIG. 4 shows a magnified cross section of the lateral part of the device of FIG. 1;

FIG. 5 shows a longitudinal section along V-V of the device of FIG. 1;

FIG. 6 is a variation of fixation of the device of FIG. 1;

FIG. 7 shows another embodiment of the device of FIG. 1; and

FIG. 8 shows a cross section of another embodiment of a device according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

A device 1 is shown with reference to FIGS. 1 to 5, for collecting solar radiation, which includes a base 2 in the shape of parallelepiped cup, which has a bottom 3 and a peripheral wall 4, which has two opposite longitudinal sides 5 and two opposite transversal sides 6, and which includes a rectangular flat cover 7, a peripheral edge of which is fixed on the peripheral edge of the peripheral wall 4, preferably in an impermeable way, so that the base 2 and the cover 7 delineate a cavity 8.

The cover 7 is made from a material transparent to solar radiation, for example, glass or plastic. The device 1 includes a longitudinal support 9 projecting into the cavity 8, which is fixed on the longitudinal median part of the bottom 3 of the cup 2. The longitudinal support includes a rectangular plate 10 extending towards the cover 7 and two symmetric opposite longitudinal rectangular flanges 11 and 12 fixed longitudinally on the free edge of the plate 10. The flanges spread longitudinally, approximately up to the opposite transversal sides 6 of the base 2 and transversely, in the direction of the opposite longitudinal sides 5 of the base 2 by being leant towards the cover 7 from the free edge of the plate 10.

The device 1 includes longitudinal flat solar collectors 15 and 16, which are fixed on the internal faces 13 and 14 of the leant flanges 11 and 12, opposite to the cover 7. The collectors include photovoltaic modules having faces sensitive to the solar radiation directed inwardly and having the inclinations of the flanges 11 and 12.

The device 1 includes two elements 17 and 18 which are fixed to the base 2 at the bottom of the cavity 8 which occupy in width and length the spaces between the plate 10 and the peripheral wall 4 of the base 2.

The elements 17 and 18 have reflecting frontal surfaces 19 and 20, which are located at a distance from the cover 7 and the collectors 15 and 16.

The reflecting frontal surfaces 19 and 20 are formed so as to reflect, at least partially, the solar radiation passing through the cover 7 respectively towards the sensitive faces of the collectors 15 and 16. The reflecting frontal surfaces 19 and 20 are preferably symmetric relative to the plate 10 of the support 9, to thus place the longitudinal plane of the device approximately in a plane passing through the North and South poles of Earth.

Preferably, the shape of the reflecting frontal surfaces 19 and 20 is adapted so that the angles of incidence of the solar radiation reflected reaching the sensitive faces of the collectors 15 and 16 are, to some extent, for at least some periods of the day and/or the year, as small as possible.

The width of the flanges 11 to 12, projecting towards the cover 7 or projecting on a plane extending above the device, may include between five and thirty percent of the width of the cavity 8. Consequently, the surface of the solar collectors 15 and 16 is approximately in the same ratio in relation to the surface of the projections of the reflecting surfaces 19 and 20 on the cover 7.

The device 1 includes electrical connectors configured to connect the solar collectors 15 and 16 to the exterior, which include wires 21 which spread along the support 9 and go outwardly passing through an orifice 3 a of the bottom 3 of the base 2.

According to one embodiment, the base 2 may be in a metal plate which does not oxidize or which is protected against oxidation, and the cover 7 may be fixed on the base 2 by a peripheral adhesive and sealing joint 22. It may be noted that the cavity 8 is sealed and only linked to the exterior or to the air through the rear orifice 3 a for routing the wires 21.

The elements 17 and 18 may include blocks, for example made of a foam plastic, covered with a layer or a sheet, for example metallic, and the reflecting surfaces 19 and 20 may include this layer or sheet by depositing thereon a layer of a reflecting material, such as silver, aluminum or zinc.

The result is that the device 1 may advantageously constitute a construction element. The aforementioned blocks may be stuck onto the bottom 3 of the base 2.

As it is shown in particular in FIG. 4, feet 23 and screws 24 may be used to fix the bottom 3 of the base 2 of the device 1 to a rear support structure 25. Likewise, two devices 1 may be coupled using, for example, feet 26 and screws 27, allowing their adjacent peripheral edges to be linked. Panels of several devices 1 may thus be made at will.

As it is shown in FIG. 6, it is also possible to form feet 23 a so that two rows of devices 1 are parallel and not located in a same plane, so as to adapt the orientation thereof relative to a particular support structure to get the nearest possible to the best orientation in relation to the light radiation.

According to the variation shown in FIG. 7, the elements 17 and 18 are replaced by shaped plates 28, peripheral edges of which are fixed flat on the internal wall of the base 2 and on the support 9, for example with screws 29. The shaped plates 28 and 29 may, for example, be metallic or of rigid plastic and their reflecting surfaces 28 a may include a deposit thereon of a layer of a reflecting matter such as silver, aluminum or zinc.

The result of the aforementioned description and in particular of the cross section view of FIG. 1 and the longitudinal section view along V-V of FIG. 5, is that the embodiment which has just been described of the device 1 according to the invention is equivalent to the juxtaposition of two “half-devices” arranged side by side, wherein a first half-device includes the solar collector 15 and the reflecting surface 19, and a second half-device includes the solar collector 16 and the reflecting surface 20. Both reflecting surfaces 19, 20 are indeed arranged symmetrically relative to a longitudinal plane of the device (shown here by the vertical rectangular plate 10), and the sensitive face of each solar collector 15, 16 spreads here above a longitudinal edge of the corresponding reflecting surface 19, 20 with an inclination angle which is determined by the orientation of the flanges 11 and 12.

As it was indicated above, each respective reflecting surface 19, 20, is conformed so that, at least during some periods of a day and some days of the year, solar radiation reflected by the reflecting surface reaches the sensitive face of the corresponding collector 15, 16, with an angle of incidence as small as possible when the device is arranged according to a predetermined orientation, for example, with its longitudinal axis arranged in a North-South direction, as indicated above.

In accordance with the properties of photovoltaic collectors, such an optimization of each reflecting surface 19, 20, to reduce as much as possible the angle of incidence of the light radiation of the sun relative to the sensitive face of each collector 15, 16, yields a better energetic efficiency of the collectors. A “better energetic efficiency” here refers to the fact that more electrical energy is supplied by the collector by unit of photovoltaic surface during preferred periods of the day and the year (periods for which the reflecting surfaces have been optimized), in relation to a collector which is arranged facing a reflecting surface of paraboloid type not optimized to be used without guiding the device relative to the sun travel. In other words, embodiments of the present invention provide to globally optimize the yearly energy supplied by the collector, i.e., the sum of all the electrical powers supplied U(t)*I(t) by the collector, instead of searching to obtain a supplied power U(t)*I(t) which is maximal in optimal conditions of use, requiring a tracking of the sun travel.

Thus, the device 1 has a lower cost price than that of a conventional solar panel, since the surface of the photovoltaic collector only represents 5% to 30% of costly photovoltaic surface, in relation to the photosensitive surface of a conventional collector without concentration.

More particularly, the shape of each reflecting surface 19, 20 is optimized by calculating the integral of the power collected during predetermined periods of the day and predetermined days of the year, so that the result of the integral, i.e., the electrical energy collected, is maximized, i.e., close to a maximum value. The reference maximum for this optimization, in terms of yearly energy, is, for example, the yearly energy supplied by a conventional flat solar collector having the same inclination and orientation as the device according to the invention, and with the same surface as the surface of the base of the device (occupied surface).

The reflecting surface obtained 19, 20 is a not parabolic shape due to the angles between reflected radiation and solar collector which change anytime (each hour and all through the year). It does not have a single focal point, but a plurality of focal points, while performing a global or “statistical” function of concentration of the solar light (yearly average), for a given orientation of the device 1 relative to Earth and for a predetermined orientation and inclination of the corresponding solar collector 15, 16 relative to the reflecting surface.

As it is shown in FIG. 1, the result of the optimization is that each reflecting surface 19, 20 may have, in a section plane perpendicular to the longitudinal axis of the collector, a first profile with no vertical axis of symmetry (the verticality being determined in relation to the mounting plane of the base 2, which cannot be horizontal in practice even if it is horizontal in FIG. 1). If the longitudinal orientation axis of the device 1 kept at the time of the design of the reflecting surfaces 19, 20 is, for example, the North-South axis, as indicated above, the reflecting surface 19 may, for example, be optimized to send towards the solar collector 15, with the smallest possible angle of incidence, the solar radiation emitted by the sun when it is directed to the West or South-West (i.e., in the afternoon in the North hemisphere), as it appears in FIG. 1. Reciprocally, the reflecting surface 20 may be optimized to send towards the solar collector 16, with the smallest possible angle of incidence, the solar radiation emitted by the sun when it is directed to the East or South-East (i.e., in the morning in the North hemisphere), as it also appears in FIG. 1.

The optimization of each reflecting surface 19, 20 may also result in each reflecting surface also having, in a longitudinal section plane parallel to the longitudinal axis of the collector, such as the section plane V-V, a profile without vertical axis of symmetry (relative to the mounting plane of the base 2), aiming to optimize the energetic efficiency taking into account the fact that the angle of the sun at noon differs according to the periods of the year.

In addition, those skilled in the art will understand that such an optimization of each reflecting surface must be made taking into account the position and orientation of the solar collector 15, 16 relative to the reflecting surface to be optimized 19, 20. In the embodiment shown in FIGS. 1 to 5, each solar collector has a predetermined inclination, imposed by the arrangement of the flanges 11 and 12. In an embodiment described hereinafter, the inclination angle is different, and consequently, the optimized shape of the reflecting surfaces may differ.

In practice, various arrangements of each solar collector in relation to the corresponding reflecting surface may be provided to facilitate the optimization of the reflecting surface. The optimization therefore relates to a couple of parameters including on the one hand, the shape of the reflecting surface and on the other hand, the orientation of the solar collector relative to the reflecting surface, for a given orientation of the device (for example, North-South). FIG. 1 shows that the arrangement of each solar collector 15, 16 relative to the corresponding reflecting surface 19, 20 is such that the solar collector is not arranged in a focal point of the reflecting surface during most hours of collection of the solar energy. This arrangement of collector relative to the reflecting surface is inherent to the fact that there is no sun tracking.

FIG. 8 shows a device 34 which differs from the device 1 in that the support 9 is suppressed. The device 34 includes a longitudinal flat solar collector 35 which is fixed flat on the internal face of the cover 7 and the sensitive face of which is turned on the side of the bottom of the base 2. It also includes two symmetric reflecting elements 36 and 37, which preferably cover the whole bottom of the base 2.

Thus, in this embodiment, the sensitive face of the longitudinal solar collector 35 is arranged above the longitudinal junction area of the first and second reflecting surfaces 36, 37. In accordance with the embodiment of FIG. 1, it may also be possible to provide two solar collectors, each being longitudinally arranged above a longitudinal edge of one of the reflecting surfaces.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims. 

1. A device for collecting solar radiation without guiding the orientation thereof relative to the sun position, the device comprising: at least one photovoltaic solar collector having a face sensitive to the solar radiation; at least one reflecting surface configured to reflect the solar radiation towards the sensitive face of the collector; and an orientation apparatus supporting the solar collector, the orientation apparatus providing an orientation and an inclination to the sensitive face of the collector in relation to the reflecting surface, the reflecting surface being conformed such that, at least during predetermined periods of a day and at least during predetermined days of a year, solar radiation reflected by the reflecting surface reaches the sensitive face of the solar collector with a minimized angle of incidence when the device is fixedly arranged in a predetermined orientation in relation to Earth.
 2. The device according to claim 1, wherein the at least one solar collector is of longitudinal shape and has a longitudinal axis thereof oriented approximately in a North-South direction.
 3. The device according to claim 1, wherein the at least one solar collector is of longitudinal shape and the reflecting surface has, in a section plane perpendicular to a longitudinal axis of the collector, a first profile with no vertical axis of symmetry.
 4. The device according to claim 3, wherein the at least one solar collector is of longitudinal shape and the reflecting surface has, in a longitudinal section plane parallel to a longitudinal axis of the collector, a second profile with no vertical axis of symmetry.
 5. The device according to claim 4, wherein the sensitive face of the at least one solar collector is disposed above a longitudinal edge of the at least one reflecting surface with a predetermined inclination angle.
 6. The device according to claim 1, wherein the at least one solar collector is of longitudinal shape, the device further comprising first and a second reflecting surfaces symmetrically arranged relative to a longitudinal plane of the device.
 7. The device according to claim 6, wherein the sensitive face of the at least one solar collector is arranged above a longitudinal junction area of the first and second reflecting surfaces.
 8. The device according to claim 6, further comprising first and second solar collectors of longitudinal shape, the first solar collector having a sensitive face thereof directed towards the first reflecting surface with a first inclination angle, the second solar collector having a sensitive face thereof directed towards the second reflecting surface with a second inclination angle.
 9. The device according to claim 1, further comprising a cavity receiving the at least one reflecting surface and wherein the at least one solar collector is fixed on a support projecting into the cavity.
 10. The device according to claim 1, further comprising a cavity receiving the at least one reflecting surface and a cover transparent to the solar radiation, covering the cavity.
 11. The device according to claim 10, wherein the at least one solar collector is fixed on the cover.
 12. The device according to claim 1, wherein a projection of the surface of the at least one solar collector into a plane above the device, is between about 5% and 30% of the projection of the at least one reflecting surface into the same plane.
 13. The device according to claim 1, further comprising a coupling apparatus configured to fix the device to at least one of another adjacent device or a structure.
 14. The device according to claim 1, further comprising an electrical connector configured to link the solar collector to an exterior of the device. 